Both sides in a debate over electronic cigarettes conceded Wednesday there's scant scientific evidence about the health effects of the devices, but that might not stop efforts in the Minnesota Legislature to regulate them like traditional tobacco products.

A series of bills to keep tabs on the new "vaping" fad have been introduced, and one got its first airing in the House Health and Human Services Committee. It would explicitly bar e-cigarettes in schools and give municipalities greater power to set sales parameters. A vote wasn't planned before evening.

"We do know enough to know that risks are here, we just don't know what they are," said the bill's sponsor, Democratic Rep. Laurie Halverson of Eagan.

About 200 shops have applied for licenses to sell the battery-powered devices in Minnesota, with 80 percent of the requests coming in the last year, said Cap O'Rourke of the Independent Vapor Retailers of Minnesota.

The thin, cylindrical devices heat a liquid nicotine solution. Users inhale a vapor but they don't emit the chemicals, tar or odor of regular cigarettes. That's so much the case that the committee's chairwoman twice warned audience members suspected of "stealth vaping" in the hearing room to knock it off.

Industry officials argue e-cigarettes pose a lower health risk than standard cigarettes and are often used as a transition tool for smokers looking to quit.

Still, public health advocates are worried. They fear e-cigarettes are being marketed to children as a gateway to nicotine addiction, noting the fruity or candy flavored liquids and devices featuring cartoon characters on the stem.

"They are clever. They are attractive. They are a drug delivery system," said Pat McKone, a tobacco control advocate at the American Lung Association in Minnesota. "The jury is out on e-cigarettes, way out."

State Health Commissioner Edward Ehlinger said the inconsistent nature of the liquid concoctions being used to fuel the vapors is troubling. "There's no way to tell what concentrations are being used," he said.

The Food and Drug Administration is conducting studies on e-cigarettes but has given no indication when findings will be ready. Republicans on the Minnesota committee suggested those urging regulations haven't made a convincing case.

But Rep. Tina Liebling, DFL-Rochester, said waiting for a conclusive verdict could subject others to involuntary exposure to the emissions in the meantime.

"Nobody is arguing we have the mountains of data that we have with tobacco," Liebling said. "Nobody here is asking to ban these devices. No one is saying adults can't use these devices in their homes, in their streets, in their friend's houses."

Another bill before the Legislature would classify e-cigarettes under the state's indoor air act, meaning they couldn't be used in public buildings, restaurants or other establishments.